1. Field of the Invention
The present invention relates to a semiconductor device and a method of assembling the semiconductor device.
2. Description of the Related Art
In a semiconductor device including a semiconductor element that generates a large amount of heat such as a CPU, it is conventional to arrange a heat sink in contact with the semiconductor element to remove the heat generated by the semiconductor element. In many cases, the heat sink is secured by screws to the substrate on which the semiconductor element is mounted.
The structure for securing the heat sink to the substrate by using screws requires laborious work for attaching the screws, thus increasing the cost. Therefore, a structure has been proposed for securing the heat sink to the substrate without using screws (see, for example, Japanese Registered Utility Model No. 3064402).
In this prior art, a holding member has a plurality of pins collectively attached thereto and an engaging member engages with the distal ends of the pins. The holding member having a plurality of pins is arranged on one side of the substrate and the heat sink, which are superposed one on another, and the engaging member is arranged on the other side of the substrate and the heat sink. The pins are inserted in the holes of the substrate and the holes of the heat sink, and the distal ends of the pins protrude from the heat sink. The protruding distal ends of the pins engage with the engaging member. Therefore, the substrate and the heat sink are held between and by the holding member and the engaging member. The engaging member includes a portion which is parallel to the heat sink and an engaging portion which is so curved as to separate away from the heat sink. The portion which is parallel to the heat sink has holes through which the pins are inserted. When the engaging member is moved transversely along the heat sink, the ends of the pins are placed on the curved engaging portion which, therefore, undergoes an elastic deformation. Therefore, the heat sink is elastically pressed onto the substrate and is attached as a unitary structure.
In the conventional structure for securing the heat sink to the substrate without using screws, the pins are fixed to the holding member, so that even after the substrate and the heat sink are assembled into a unit as a semiconductor device, the holding member remains secured to the pins forming part of the semiconductor device. Therefore, holding members having a plurality of pins must be provided in a large number, resulting in an increase in the cost and an increase in the weight of the semiconductor device. When the holding member has a large outer shape, the semiconductor device assumes a correspondingly large outer shape. Besides, the movable engaging member may cause the position of the pins to be moved if an external force, such as vibration or shock, is exerted thereon.